Galvanizing furnace



Jan. 20, 1925.

I W. G. IMHOFF GALVANIZING FURNACE Filed June 7.

1923 5 Sheets-Sheet 1 ,FIG. I.

V INVENTOR Wallace G. Imhofl- 1, WM raewaa w. G. IMHOFF GALVANIZING FURNACE Filed June 1925 s Sheets-Sheet 2 nvvnvran 7 Wallace G. Irnhol'} h s at tar-1784 J 20, 1925. 1,523fi47 W. G. IMHOFF GALVANI ZING FURNACE Filed June 1923 5 Sheets-$heet INVENTDR We. "ace G. I m/2a 17. i6 ditarrrlu Jan. 20, 1925 w. ca. lMHOFF GALVANI ZING FURNACE Filed June '7 1323 5 Sheets$heet 5 FIG ; Wailae- G Irv/20)} Patented Jan." 20, 1925.

UNITED STATES PATENT OFFICE.

WALLKCE G. IMHOFF, 0F PITTSBURGH. PENNSYLVANIA. ASSIGNOR TO WARREN S. SMITH, OF NEW YORK, N. Y.

GALVANIZING FURNACE.

Application filed June 7,

To all whom it may concern:

Be it known that I, VVALLAce G. IMHOFF, a citizen of the United States, residing at Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in a Galvanizing Furnace, of which the following is a specification.

This invention relates to a furnace for use in hot galvanizing.

Several difiiculties are encountered in the fire'heating of galvanizing kettles to provide va hath suitable for hot galvanizing.

One difiiculty has been local overheating of the kettle. This is of common. occurrence, and is largely due to the arrangement necessarily employed for fire-heating a kettle in which the hot products of the combustion of coke. coal, oil, gas, or the like,

are admitted to the galvanizing kettlh by way of tports or fines in the refractory material o the setting adjacent to the lower portion of the kettle.

Another ditliculty has been general overheating of the kettle. In using a galvanizing kettle from day to day it is kept continuously heated, but is used for less than half of each day. During the night, or at any time when the furnace is not under con tinuous observation, the tire may rise to an extent sutiicient to produce overheating ot the kettle.

It is a fact. that when molten zinc is in contact with iron or other metal the molten zinc exercises a solvent action upon the metal with which it is in contact, forming a zinc alloy known as dross. This action results in the more or less rapid destruction of the galvanizing kettle which contains the bath of molten zine. It is also a known fact that overheating greatly accelerates the torn'iation of dross and the destrnction of the kettle. this action being particularly marked at temperatures above 900 Fahrenheit.

Another ditiicultv with the fire-heated galvanizing furnace commonly in use is that of maintaining a line regulation of the temperature of the galvanizing bath (hiring the actual galvanizing operations. The bath must be held at the most desirable tcmperature for the particular article being galvanized under the general operating con- 1923. Serial N0. 643.956.

ditions, and the rate at which heat is abstracted from the bath.

One object of the present invention is to provide a galvanizing kettle in which the entire heating etlect. is distributed uniformly over the area of the galvanizing kettle to be heated, thus preventing any pos 'sibility of local overheating of any portion of the kettle.

Another object of the invention is to provide a galvanizing furnace in which the temperature to which the galvanizing kettle is raised may be set at a definite and unvarying point, thus preventing general overheating of the kettle.

A-further object of the invention is to provide a galvanizing furnace in which the temperature of the kettle and the bath contained therein may be maintained under full and accurate control during the continuance of galvanizing operations. These objects are attained by providing a'ggalvanizing furnace in which the kettle is electrically heated, the electric heating means of the furnace being so arranged as to distribute the. heating etlect uniformly over the. area of the kettle to be heated, and under such control that the temperature of the kettle and the bath therein may be set at a definite point, and may be maintained during the abstraction of heat from the bath in the kettle.

In the accompanying drawings Figure l is a vertical longitudinal section through a preferred form ofthe furnac of the present invention, such section being taken on the line 11 Figure 2: Figure 2 is a cross sectional view of the same form of furnace taken'on the line 22 of Figure 1; Figure 3 is a wiring diagram showing all the resistance units of the circuit connected in straight scrics throughout: Figiirc t is a Wiring diagram showing the resistance coils of the arrangement illustrated in Figures 1 and 2 connected in pairs, with the two units of each pair in parallel and the two pairs connected in two independent circuits; Figure 5 is'a wiring diagram showing one resistance unit. cut out of the circuit and the other resistance units connected in series; Figure 6 is a detail elevation of resistance units of modified form; Figure 7 is a section on line 7-7 Figure 6; Figure 8 is an elevation of another modified form of unit; Figure 9 is a section on line 99 Figure 8; and Figure 10 is a cross sectional view through a-form of the invention in which the-kettle is'heated by't-he inductive ctl'cet of an alternating electric current.

Referring to Figures 1 and 2 of the drawings, reference numeral 1 designates the furnaeesetting which is preferably composed of a good grade of tire brick. \Vithin set' ting l is a continuous wall 2 of heat insulating brick; and within heat insulating wall 2 is the galvanizing kettle 3, which is commonly made of tire-box steel orotber suitable metal.

The resistaure units which are designated generally by the reference numeral 4, comprise coils of wire made of some alloy such as nichronuwhich ollers relatively great resistance to the passage of an electric rurrent. 'lhcsc resistance units. or resistors, ex tend completely around the galvanizing kettle 3 and embrace it eloselv. For the sake of convenience. the resistors 1' are desirably imbedded in a eastv ot' a refractory cement, such as alundnm cement or asbestos cement, which forms a casing for the kettle proper. The space between the cast and the heat insulating wall 2 may he provided as shown, with a filling U of powdered i'nugnesia, orthe like, in order to provide perfect heat insulation for the kettle.

It should he noted that the. number and spacing of the resistors 4 is sueh that their heating effect is distributed uniformly over the area of the kettle which they beat.

As shown inFigure l, the uppermost unit A of the resistors eonnects witlrtcrminal wires (1 and a, which form a" circuit through the resistor. The next resistor ll connects with terminal wires 7) and II. the next resistor C with terminal wires and c.

.and the lowermost resistor D conne ts with terminal wires d and d.

lVith reference to the wiring diagram shown in Figure I) of the drawings. the line wires are designated by the referci'iee numorals 8 and 9. In a shunt. lOof the line. and controlled by a switch 11 is a resistance 12. This resistance l-Z may take any desired form. such as a resistance box. water rheostat, or any similar device. An ammetier 1? is also desirably provided in a shunt l'l having therein a switch 15.

As shown in this diagramxall the rcsistors A, ll, C, and D of the circuit. are connected in series. in such arrangementeurrent passes by way of lead-in wire 8 and wire a tothe resistor A. the double switch 16 and switch 17 being closed to complete the circuit. From resistance A the current asses by way of wire rt, the switch 18 bemg open, to the wire 7) leading to resistance B. From resistor B, the switches 19 and 20 being closed, the current-passes through wire 6 to wire 0 leading to the resistor C. From resistor C, the switch 21 being open, the current passes by wires 0' and (l to the lowermost resistor D. From resistor I), switch 2 2 being closed, the currentpasses out to the line. i

Figure 4 of the drawings shows a wiring diagram in which the resistors A and B are connected in parallel and the resistors C and D are connected in parallel, the two pairs thus "forming two independent series parallel circuits. In this arrangement current flowing through the lead in line 8 flows by way of wires :1. and I) to both the re sistors and 13, double throw switch 19 being thrown to interconnoetv these two wires. tter passing through. the resistors A and ll the current flows into the return line 3) by way of switch 18, whi h i:: closed.

in this arrangement of the ltsistrds the current is divided on the line, and a por tion thereol' llows through the auxiliary limwires lit and ill to the resistors (l and l), which are also connected in parallel. shunt 125' of these auxiliaryjine wires is connected :1 ltSlStuure 26. this .slumt being controlled b a switch 1']: and in another shunt ot the wire; 2; connected an amiuetcr 25 this shunt tllry controlled by a. switch iitl. l ronrthe. lead in wire 23 of the line current flows by way of wires r" and (I. switch 21 being' clo ed. t the resistors and ll. From resistors (l and D current lows by way of wires 0 and ll to the return wire 24 of the. auxiliary line switch 22 being closed, and thence hack to the main line.

in the wiring diagram shown in Figure 5 of the drawings the conne tions are similar to those shown in Figure 3 thereoi c.\- rept; that a double switch ill i thrown to disconnect wires c and (I and to return rur' rent by way of an auxiliary return wire l) to the main line. A switch i i-l is also open so that wire. (1" is not. connected with auxiliar return wire 32. in this arrangement the resistors A. B. and C are rouurrtrd in series. and the resistor D is cut. out conipletelv from the circuit.

it will be understood that, every eleirient shown in each of the diagrams does not appear on each of the other diagram There may also be numerous other conn ctions n the switehl'ioard employed. Certain of the switches shown may further be utilized to cut additional resistors out of the circuit in the same manner shown and described for cutting the lowermost resistor I) out of the circuit. It is obviously unnecessary that all such additions, modifications. and arrangements be shown as they obviously fall within the knowledge and capabilities of a skilled electrician. and the. showin of the diagrams is illustrative merely of t e mannor in which the distribution and intensity 1 in :r

of the heating effect produced by the electric current may be regulated to secure the desired heating of the galvanizing kettle.

In conducting actual hot galvanizing opcrations the temperature of the bath is preferably maintained at a temperature of from 820 Fahrenheit to 850 Fahrenheit. \Vhen the kettle is not inactual use but it is desired to maintain a bath which may be used instantly or rapidly raised to the desired temperature. the heating is preferably 5o regulated that the temperature of the bath is maintained at from 800 Fahrenheit to 820" Fahrenheit in order to secure convenience in conducting the galvanizing process with a minimum deterioration of the galvanizing kettle.

The greater-variations in the temperature of the galvanizing kettle may be effected the manner of connecting the resistors in the circuit, and the lesser variations by utilization of the line resistance unit or units, such as resistance boxes or rheostats.

It. therefore, the resistors are connected in series, as shown in the diagram of Figure 3, and it is desired to raise the temperature of the galvanizing kettle, the connections,

may be so changed as to parallel the resistors in pairs. Also, if so desired. all the resistors may be connected in parallel to further increase the heating effect of the ciredit.

If the heating eli'ect is to be decreased from that produced when the resistors a e all in series, the current may be further regulated by throwing the rheostat in the circuit. In leaving: the kettle heated, but: idle, the resistance coils of the circuit are arranged in the desired manner and the line resistance is so arranged that the temperature of the bath is maintained at the proper temperature. I

If so desired, a thermostatic, or other automatic resistance of any well known type, may be interposed in the line to maintain the temperature of the kettle automatically at a certain point.

Instead of the coiled wire resistors 4, resistors of other types, as for example the hairpin form of nichrome resistor 34 shown in Figure 6 of the drawings or the carbon resistance blocks 34' shown in Figure 8 of the drawings. may be employed. When resisters of such other form are used, they may be connected in cincuit in the same manner as the resistors 4 which have been described above.

With the form and arrangement of the furnace as described above. it is to be assumed that the line supplying electricity to the furnace carries a direct current. The form of the furnace shown in Figure 10 of the drawings is, however, designed for use with an alternating current. In the form of the device illustrated in Figure 10 the gelvanizing kettle 35 is set in a furnace comprising an outer wall 36 of tire brick, and an Inner Wall 37 of heat insulating material immediately adjacent the kettle. Between outer wall 36 and inner wall 37 is a filling of cementitious material in which the current carrying coil 38 is imbedded. Layers or walls 39 of electrical insulating material are disposed on both sides of the coil 38 and the filling material in which it is imbeddcd.

The coil 38 itmlf is formed of a plurality of turns'of tubing composed of some material. such as copper. which is a good con doctor of electricity. llach turn of the coil extends completely around the galvanizing kettle 35. and is kept cool by means of water passing through the tubing of the coil. The heating effect in thismodified form of the furnace is supplied by the induced currents produced by alternations of the current in coil 38. The coil itself is protected from the heat by the inner heat insulating wall 37 land by the water flowing through the col It will be understood that the heating effect of the current may be regulated by any well known electrical means for such purpose, and that such regulation is a simple matter because the conducting means of the furnace comprise a single continuous coil.

Certainobvious advantages of the device have beenstated above, but other advantages incident to itsfundamental idea and arrangement will readily be appreciated by those skilled in the art to which the invention pertains. It will also be understood that the device is susceptible of numerous modifications over the form and arrangement illustrated and described herein, and the scope of the invention is therefore to be restricted onlv by the limitations contained in the appended claims.

' What I claim is:

1. In a furnace for hot galvanizing the combination of a metallic galvanizing kettle with an electric resistance circuit for supplying heat thereto, means forregulating the current passing through such resistance circuit. and means for regulating the heating effect of the current supplied.

2. In a furnace for hot galvanizing the combination of a metallic galvanizing kettle. with an electric resistance circuit comprising a pluralityof resistors for sup plying heat to saidkettle, and meansv for connecting the several resistors of said circuit in series or in parallel for regulating the heating effect of the circuit.

3. In a furnace for hot galvanizing the combinationof a galvanizing kettle with an electric resistance circuit comprising a plurality of resistors for supplying heat-t0 said kettle. and means for cutting out resistors from the circuit and for connecting the resistors in series or in parallel to regulate the heating effect of the circuit.

4. In a furnace for hot galvanizing the combination of a galvanizing kettle with an electric resistance circuit imbedded in ccnientitious material to form a casing enibracing said kettle and comprising a plurality of resistors for supplying heat to said kettle. and means for connecting the resistors of said circuit in series or in parallel for regulating the heating elt'ect of the circuit.

5. in a furnace for hot galvanizing the combination of a galvanizing kettle with a heat insulating setting therefor, and electrical means disposed between the setting and the kettle arraiugcd to exert upon the. latter a heating etl'ect distributed uniformly over the area of the kettle to be heated.

(S. In a furnace for hot galvanizing the combination ota galvanizing kettle with a heat: insulating setting therefor. and electric resistors disposed between the setting and the kettle and arranged to exert a uniformly distributed heating effect. over the area of the kettle tobc heated.

7. In a furnace for hot galvanizing the combination of agalvanizing kettle with a heat insulating setting therefor, and an electric circuit disposed between the setting and the kettle 'and arranged to exert a unifornily distributed heating effect over the area of the kettle to be heated.

S. In a furnace for hot galvanizing the combination of a galvanizing kettle with a heat insulating setting therefor, and an electric resistance circuit disposed between thesetting and the kettle and arranged to exert a uniformly distributed heating effect over the arcaoi' the kettle to be heated.

9. In a furnace for hot galvanizing the combination of a metallic galvanizing kettle with an electric resistance circuit comprising a plurality of resistors arranged to exert a uniformly distributed. heating etlcct over the area of the kettle to be heated. and means for connecting the resistors in series or in parallel for regulating the heatging etlcct of the circuit.

10. in a 'l'urnace for hot galvanizing the combination ot a galvanizing kettle with an electric circuit imbeddcd in ccinentitious material to form a casing arranged to cuibrace the kettle for supplying heat thereto. said circuit being so arranged that the heating cfiect' thereoi is distributed uniformly over the arm: of the kettle to be heated.

H. in a furnace. for hot galvanizing the combination of a galvanizing kettle with an electric resistance circuit comprising a plurality of resistors imbedded in cementititais material to form a casing arranged to embrace said kettle and supply heat thcrcto said resistors being so arranged that the heating efi'ect thereof is distributed uniformly over the area of the kettle to be heated.

In witness whereof, I hereunto set my hand.

WALLACE G. IMHOFF. Witnesses:

E. B. \VALTEns, R. M. GAUGHAN. 

